On the item page there is a button labeled "Track this auction". It will add the auction to a list of auctions that you are interested in. It allows you to keep track of an auction easily, so you don't have to search for it every time you want to check if you still have the bid. There is also an option in the user settings to receive a notification whenever you lose the bid on a tracked auction. It's on by default, but you can switch it off.

To see the list of tracked auctions, click on "Tracked auctions" in the user part of the menu. It will only show if you're logged in. You can untrack auctions from this list by ticking the selection box and clicking "Untrack selected items". You can't stop tracking auctions that you have the bid on. If an item disappears from your tracked list, it got sold or it expired and you didn't have the highest bid.

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